This commit changes the behavior of the builtin SSHRun action to use a Windows shell if the WinSSH communicator is active. This allows for running one-off SSH commands with Windows Command Prompt or PowerShell. By default, this will not allocate a TTY for any SSH commands. Example usage: ``` vagrant ssh -c 'dir "c:\program files"' ``` Updates docs to reflect a change made in a55a53e6a46438d5093487f83248f01ddece4534.